The internal makeup of octopus and squid is also unique to each cephalopod. The copper is what helps transport oxygen within the animals’ bodies and makes their blood blue. Interestingly, both have squirt ink and copper in their blood. Squid eyes are embedded in the head between the tentacles and mantle of the body. Octopus eyes protrude from the top of the head, bulging near the tentacles. The eyes of the octopus and squid are also placed differently. You’ll also notice that a squid has two fins on their head, while the octopus has no fins at all-except for some deep-water species like the Dumbo octopus, which was named for the ear-like fins on its head that resemble the large, floppy ears of Disney’s Dumbo (the elephant).īoth squids and octopuses have suckers on their arms, but the two extra tentacles on squids are equipped with specialized hooks and sucker rings with teeth attached. The squid has a triangular head, eight arms in the rear, two extra long tentacles, a long body, and a bony plate called a “pen” that’s a vestigial remnant of its mollusk shell. The octopus has a round head and eight arms that radiate from it like the spokes of a wheel. Squids and octopuses are built similarly, but you can tell they’re different creatures just from their appearance. And, unlike other mollusks, neither one has a shell. They’re also both invertebrates and mollusks, and they both have eight arms. Biological Classificationīoth squids and octopuses are cephalopods, which means “head-footed” as they have no real feet and their head is their most prominent feature. To help you understand the differences between squid vs octopus better, we’ll describe their differences and similarities when it comes to biological classification, anatomy, size, lifespan, habitat, and hunting behavior.

Octopus arms vs tentacles